The project was extended this year to analyze the mode of action of pertussis toxin (Ptx). This component of the Bordetella pertussis bacteria was shown in another study to exhibit an outstanding adjuvant capacity, manifested by the enhancement of induction of experimental autoimmune uveoretinitis (EAU) in rats. In order to learn about the immunostimulatory activity of Ptx, its effects on lymphocytes and macrophages in vitro were determined: these cells are responsible for EAU development. The main findings: (1) Ptx stimulates proliferation of lymphocytes from human donors or various experimental animals. (2) Lymphocytes stimulated with Ptx also increase the production of various mediators ("lymphokines"), including interleukins (IL)-2 and -3. (3) Ptx stimulates the production and release of IL-1 by human monocytes or mouse peritoneal macrophages. The stimulaory effects of Ptx on lymphocytes and macrophages in culture may be related to its adjuvant activity. However, the optimal concentrations of Ptx for the effects in vitro were considerably higher than those producing the effect in vivo.